18F-FDG PET/CT for detection of the primary tumor in adults with extracervical metastases from cancer of unknown primary: A systematic review and meta-analysis

Utility of 18F-FDG PET/CT in Treatment Strategies for Patients With Cancer of Unknown Primary: A Single-Center, Retrospective Change-in-Management Study

Background

Cancer of unknown primary (CUP) is difficult to diagnose and classify clinically, and the disease develops rapidly. Therefore, the primary tumor detected in patients with CUP plays a profound role in the diagnosis and treatment of patients. The search for the primary tumor of CUP is also one of the indications for 18F-fluoro-2-deoxyglucose-positron emission tomography and computed tomography (FDG-PET/CT). Our objective was to evaluate the role of 18F-FDG PET/CT imaging in primary tumor detection and treatment formulation in patients with CUP.

Methods

Sixty-two patients with CUP were selected from a database consisting of 18 802 cases in the Jiangsu Cancer Hospital PET/CT center from May 18, 2016 to November 18, 2022. Clinical data and changes in treatment strategies before and after PET/CT were collected.

Results

A total of 42 primary tumors (42/62, 67.7%) were identified by PET/CT examination. The tumor staging of patients before conventional PET/CT imaging (such as CT/magnetic resonance imaging [MRI]/US) and after PET/CT did not change in 28 patients (28/62, 45.2%), whereas for 34 patients (34/62, 54.8%), tumor staging changed. Forty-five patients (45/62, 72.6%) had not developed treatment plans before PET/CT examination, but treatment plans were clarified after PET/CT examination. Thirteen patients (13/62, 21.0%) underwent changes in treatments before and after PET/CT examination. Among the 20 patients (20/62, 32.3%) whose primary tumors were not detected, 16 patients (16/20, 80.0%) had no treatment plans before PET/CT and the treatment plans were defined after PET/CT, 3 patients (3/20, 15.0%) changed the treatment plans before and after PET/CT, and 1 patient (1/20, 5.0%) did not change the treatment plan.

Conclusions

The 18F-FDG PET/CT plays an important role in the detection and staging of primary tumors in patients with CUP. The PET/CT findings can not only help clinicians develop appropriate treatment plans for patients with CUP but also serve as an effective approach to improve real-life treatment strategies for these patients.

2-[18F]FDG-PET/CT in Cancer of Unknown Primary Tumor-A Retrospective Register-Based Cohort Study

We investigated the impact of 2-[18F]FDG-PET/CT on detection rate (DR) of the primary tumor and survival in patients with suspected cancer of unknown primary tumor (CUP), comparing it to the conventional diagnostic imaging method, CT. Patients who received a tentative CUP diagnosis at Odense University Hospital from 2014-2017 were included. Patients receiving a 2-[18F]FDG-PET/CT were assigned to the 2-[18F]FDG-PET/CT group and patients receiving a CT only to the CT group. DR was calculated as the proportion of true positive findings of 2-[18F]FDG-PET/CT and CT scans, separately, using biopsy of the primary tumor, autopsy, or clinical decision as reference standard. Survival analyses included Kaplan-Meier estimates and Cox proportional hazards regression adjusted for age, sex, treatment, and propensity score. We included 193 patients. Of these, 159 were in the 2-[18F]FDG-PET/CT group and 34 were in the CT group. DR was 36.5% in the 2-[18F]FDG-PET/CT group and 17.6% in the CT group, respectively (p = 0.012). Median survival was 7.4 (95% CI 0.4-98.7) months in the 2-[18F]FDG-PET/CT group and 3.8 (95% CI 0.2-98.1) in the CT group. Survival analysis showed a crude hazard ratio of 0.63 (p = 0.024) and an adjusted hazard ratio of 0.68 (p = 0.087) for the 2-[18F]FDG-PET/CT group compared with CT. This study found a significantly higher DR of the primary tumor in suspected CUP patients using 2-[18F]FDG-PET/CT compared with patients receiving only CT, with possible immense clinical importance. No significant difference in survival was found, although a possible tendency towards longer survival in the 2-[18F]FDG-PET/CT group was observed.

[Positron emission tomography in CUP syndrome]

CLINICAL/METHODOLOGICAL ISSUE

In approximately 2% of all cancers, no primary tumor can be detected and cancer of unknown primary (CUP) syndrome, a diagnosis of exclusion, is made.

STANDARD RADIOLOGICAL METHODS

In CUP syndrome, computed tomography (CT) and/or magnetic resonance imaging (MRI) do not lead to the detection of primary tumors.

METHODOLOGICAL INNOVATIONS

In the advanced diagnostic workup of CUP syndrome, ¹⁸F‑fluordeoxyglucose positron emission tomography/computed tomography (¹⁸F‑FDG PET/CT) can be used. In addition, ⁶⁸Ga-fibroblast activation protein inhibitor (FAPI) PET/CT as a novel, experimental imaging technique may be considered.

PERFORMANCE

¹⁸F‑FDG PET/CT is clinically established for the detection of primary tumors of cervical CUP syndrome. High detection rates have also been reported for ¹⁸F‑FDG-PET/CT in extracervical CUP syndrome. ⁶⁸Ga-FAPI PET/CT has not yet been clinically established, but remarkably high detection rates have been shown for ¹⁸F‑FDG-negative cervical CUP syndrome due to its low background activity.

ACHIEVEMENTS

The benefit of ¹⁸F‑FDG PET in CUP syndrome has been documented in several meta-analyses. To date, the evidence for the use of ⁶⁸Ga-FAPI PET/CT in CUP syndrome is still rudimentary.

PRACTICAL RECOMMENDATIONS

¹⁸F‑FDG PET should be applied regularly in cervical CUP syndrome and can be individually considered in extracervical CUP syndrome.

Multiple recurrences of unknown primary tumor in a meningioma: A case report

Metastasis of a systemic tumor into a primary brain tumor has been rarely reported in the literature. These metastases could be seen mostly in meningiomas and in less frequently in the other intracranial tumors. Carcinoma of an unknown primary site (CUP) metastasizing into an intracranial meningioma is not a common occasion. According to the best of our knowledge, in this report, we present the first case with multiple recurrent CUP, which metastasized to intracranial meningioma, reported in the literature. The whole body was investigated with FDG PET/CT and biomarkers of the most common carcinomas for primary cancer. However, these tests showed no primary affected region. Despite all adjuvant therapies, the tumor had multiple recurrences. Such cases are still a challenge to offer optimal management.

Carcinoma of Unknown Original Identified as Renal Cell Carcinoma by 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Scan: A Report of Two Cases

Imaging is useful in identifying the primary site of an unknown primary cancer, and ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) is an excellent imaging modality for identifying the primary lesion. However, a potential limitation is that ¹⁸F-FDG is physiologically excreted from the kidneys, thus masking renal lesions. In this report, we describe two cases of cancer of unknown origin that were detected as originating from renal cancer on ¹⁸F-FDG PET/CT. Both cases showed abnormal nodular accumulation of ¹⁸F-FDG in the kidney, which can be distinguished from the physiological excretion of ¹⁸F-FDG in the urinary tract. It is clinically crucial to be able to confirm the possibility of renal cancer, and careful observation of the urinary tract with ¹⁸F-FDG PET/CT can be useful.

A multicentre retrospective study comparing site-specific treatment with empiric treatment for unfavourable subset of cancer of unknown primary site

BACKGROUND

Patients with cancer of unknown primary site are divided into two distinct groups, favourable and unfavourable subsets. For the unfavourable subset, empiric treatment or site-specific treatment is recommended, but limited knowledge exists about the efficacy of site-specific treatment compared with empiric treatment in clinical practice.

METHODS

In this multicentre retrospective study, we reviewed the medical records of patients with cancer of unknown primary site treated with chemotherapy (or chemoradiotherapy) as first-line treatment from eight institutions during 2006-18. We investigated the workup modality and categorized the patients into favourable and unfavourable subsets, which were further divided into site-specific and empiric treatment groups. Site-specific treatment is defined as a standard chemotherapy for an estimated primary site. We examined the efficacy in the favourable and unfavourable subsets and performed multivariable analysis for estimating the overall survival in the unfavourable subset.

RESULTS

Of 177 patients with cancer of unknown primary site, 33 and 144 were categorized into favourable and unfavourable subsets, respectively. In the unfavourable subset, 84 patients (58.3%) received empiric therapy, and 60 patients (41.7%) received site-specific treatment. Median overall survival was 10.0 and 10.1 months in site-specific and empiric treatment groups, respectively, with no significant difference (hazard ratio 1.01, 95% confidence interval 0.70-1.45, P = 0.95). Multivariable analysis revealed performance status, number of metastatic sites and hypoalbuminaemia as independent prognostic factors for overall survival in the unfavourable subset.

CONCLUSIONS

Overall survival in site-specific and empiric treatment groups was similar in the unfavourable cancer of unknown primary site subset in this study. Further research is needed to prolong overall survival in patients in the unfavourable cancer of unknown primary site subset.

Real-Life Performance of F-18-FDG PET/CT in Patients with Cervical Lymph Node Metastasis of Unknown Primary Tumor

Background: Neoplasms in the head and neck region possess higher glycolytic activity than normal tissue, showing increased glucose metabolism. F-18-Flourodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) can identify an unknown primary tumor (CUP). Aim: The aim of this study was to assess the real-life performance of F-18-FDG-PET/CT in detecting primary sites in patients with cervical lymph node metastasis of CUP. Methods: A retrospective data analysis of 31 patients who received FDG-PET/CT between June 2009 and March 2015 in a CUP context with histologically confirmed cervical lymph node metastasis was included. Results: In 48% of the patients (15/31), PET/CT showed suspicious tracer accumulation. In 52% of the patients (16/31), there was no suspicious radiotracer uptake, which was confirmed by the lack of identification of any primary tumor in 10 cases until the end of follow-up. FDG-PET/CT had a sensitivity of 67%, specificity of 91%, PPV of 92%, and NPV of 63% in detecting the primary tumor. Additionally, PET/CT showed suspicious tracer accumulation according to further metastasis in 32% of the patients (10/31). Conclusion: FDG-PET/CT imaging is a useful technique for primary tumor detection in patients in a cervical CUP context. Furthermore, it provides information on the ulterior metastasis of the disease.

Clinicopathological, molecular and prognostic characteristics of cancer of unknown primary in China: An analysis of 1420 cases

BACKGROUND

Cancer of unknown primary (CUP) is defined the presence of metastatic disease without an identified primary site. An unidentifiable primary site of cancer creates significant challenges for treatment selection. We aimed to describe the clinicopathological, molecular, and prognostic characteristics of Chinese CUP patients.

METHODS

Patients with oncologist-confirmed CUP were identified at Fudan University Shanghai Cancer Center from 2019 to 2020. Information on patient characteristics, tumor presentation, treatment, and outcome were retrospectively collected from the inpatient database and pathological consultation database for descriptive analysis. A multivariable logistic regression model was established to identify factors associated with patient prognosis.

RESULTS

A total of 1420 CUP patients were enrolled in this study. The baseline characteristics of the entire cohort included the following: median age (59 years old), female sex (45.8%), adenocarcinoma (47.7%), and poorly differentiated or undifferentiated tumors (92.1%). For the inpatient cohort, the most common sites where cancer spread included the lymph nodes (41.8%), bone (22.0%), liver (20.1%), and peritoneum/retroperitoneum (16.0%). A total of 77.4% and 58.2% of patients were treated with local therapy and systemic therapy, respectively. Four prognostic factors, including liver metastasis, peritoneal/retroperitoneal metastasis, number of metastatic sites (N ≥ 2), and systemic treatment, were independently associated with overall survival. Additionally, 24.8% (79/318) of patients received molecular testing, including PD-L1, human papillomavirus, genetic variation, and 90-gene expression tests for diagnosis or therapy selection.

CONCLUSION

Cancer of unknown primary remains a difficult cancer to diagnose and manage. Our findings improve our understanding of Chinese CUP patient characteristics, leading to improved care and outcomes for CUP patients.

Effect of Whole-body [18F]Fluoro-2-deoxy-2-d-glucose Positron Emission Tomography in Patients with Suspected Brain Metastasis

Background and Purpose [18F]Fluoro-2-deoxy-2-d-glucose (FDG) positron emission tomography/computed tomography (PET/CT) has a promising role in the workup and management of carcinoma of unknown primary (CUP). We have evaluated the effect of whole-body FDG PET/CT in assessing the patients presented with suspected brain metastasis (CUP-BM) on brain magnetic resonance imaging (MRI) or computed tomography (CT).

Materials and Methods This retrospective study included FDG PET/CT of 50 patients (24 males, mean: 58 ± 12.2 years old) with a CUP-BM diagnosis based on MRI and CT imaging. The final diagnosis of primary brain neoplasm (BP) or brain metastases (BM) was based on FDG PET/CT findings and/or histopathology (HPE).

Results On FDG PET/CT, 52% (26/50) of patients did not have any systemic lesion apart from a brain lesion. Out of these, 50% (13/26) had HPE confirmation of primary brain neoplasm (BP). FDG PET/CT identified multiple systemic lesions apart from brain lesions in the remaining 48% (24/50) of patients. They were categorized as the brain metastases (BM) group. The primary lesions were located in the lungs (n = 20), kidneys (n = 1), prostate (n = 1), esophagus (n = 1), and tongue (n = 1).

Conclusion FDG PET/CT could suggest a diagnosis of BM based on the presence of systemic lesions. It also provides an easily accessible peripheral site for biopsy and systemic disease burden in a single scan. FDG PET/CT's up-front use in suspected CUP-BM on CT and/or MRI could differentiate the BM from BP in most cases and avoid brain biopsy in the BM group.

Clinical validation of a 90-gene expression test for tumor tissue of origin diagnosis: a large-scale multicenter study of 1417 patients

Background

Once malignancy tumors were diagnosed, the determination of tissue origin and tumor type is critical for clinical management. Although the significant advance in imaging techniques and histopathological approaches, the diagnosis remains challenging in patients with metastatic and poorly differentiated or undifferentiated tumors. Gene expression profiling has been demonstrated the ability to classify multiple tumor types. The present study aims to assess the performance of a 90-gene expression test for tumor classification (i.e. the determination of tumor tissue of origin) in real clinical settings.

Methods

Formalin-fixed paraffin-embedded samples and associated clinicopathologic information were collected from three cancer centers between January 2016 and January 2021. A total of 1417 specimens that met quality control criteria (RNA quality, tumor cell content ≥ 60% and so on) were analyzed by the 90-gene expression test to identify the tumor tissue of origin. The performance was evaluated by comparing the test results with histopathological diagnosis.

Results

The 1417 samples represent 21 main tumor types classified by common tissue origins and anatomic sites. Overall, the 90-gene expression test reached an accuracy of 94.4% (1338/1417, 95% CI: 0.93 to 0.96). Among different tumor types, sensitivities were ranged from 74.2% (head&neck tumor) to 100% (adrenal carcinoma, mesothelioma, and prostate cancer). Sensitivities for the most prevalent cancers of lung, breast, colorectum, and gastroesophagus are 95.0%, 98.4%, 93.9%, and 90.6%, respectively. Moreover, specificities for all 21 tumor types are greater than 99%.

Conclusions

These findings showed robust performance of the 90-gene expression test for identifying the tumor tissue of origin and support the use of molecular testing as an adjunct to tumor classification, especially to those poorly differentiated or undifferentiated tumors in clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03318-6.

Diagnostic efficiency of PET/CT in patients with cancer of unknown primary with brain metastasis as initial manifestation and its impact on overall survival

Background

Carcinoma of unknown primary (CUP) is a diagnostic and therapeutic challenge; correct diagnostic approach results in better outcomes in patients with brain metastasis. Whole body 18 F-FDG PET/CT is a helpful modality to detect the origin of primary tumor and assess metastasis in the rest of the body. We assessed the value of PET/CT in detection of unknown primary in 39 patients with brain metastases as initial presentation and detected its impact on their overall survival.

Results

PET/CT could correctly detected the primary tumor in 49% of patients which occurred mainly in the lung, 63% of patients had additional extracerebral metastatic sites mostly in lymph nodes. Specificity, sensitivity, and accuracy of PET/CT in CUP patients were 95%, 79%, and 87%, respectively. No significant difference was noticed in estimated overall survival time between patients with an identified primary tumor and patients with unidentified primary tumor.

Conclusion

PET–CT was a helpful non-invasive imaging modality in detecting primary in CUP patients with metastatic brain lesion. It helped in the diagnosis of unexpected extracerebral metastatic lesions. However, the identification of the primary tumor by PET/CT has no significant prognostic effect on patient overall survival.

Impact of 18F-Fluorodeoxyglucose positron emission tomography on management of cancer of unknown primary: systematic review and meta-analysis

BACKGROUND

Cancers of unknown primary (CUP) have traditionally been treated empirically, with a dismal prognosis. Compared with standard diagnostic tests, including CT and MRI, imaging with ¹⁸F-fluorodeoxyglucose (FDG) PET or PET/CT has shown the capacity to better identify the primary tumour site and detect additional sites of metastasis. However, its clinical impact is not well established. We performed a systematic review and meta-analysis of prior studies to assess the impact of FDG-PET or PET/CT on the management of patients with CUP.

MATERIALS AND METHODS

Pubmed and EMBASE databases were searched up to 4th February 2021. Studies that reported the proportion of patients with CUP who experienced a management change after FDG-PET or PET/ computed tomography (CT) were included and the proportions were pooled using the random-effects model. Study quality was assessed using QUADAS-2. Subgroup analysis was conducted to explore heterogeneity.

RESULTS

Thirty-eight studies (involving 2795 patients) were included. The pooled proportion of patients with management changes was 35% (95% confidence interval 31%-40%). There was substantial heterogeneity among the studies (Q-test, p < 0.01; I² = 82%). The specific reason for management change was more commonly detection of the primary site (22% [95% CI 18-28%]) than detection of additional metastatic sites (14% [95% CI 10-19%]). The pooled proportions of patients with management changes were similar among numerous subgroups (range, 32.8%-38.2%).

CONCLUSION

FDG-PET or PET/CT had a meaningful impact on the management of patients with CUP. Approximately, a third of patients had their management changed because of FDG-PET or PET/CT results, and this finding was consistent across numerous subgroups.

The usefulness of [18F]FDG-PET/CT in detecting and managing cancers with unknown primary site depends on histological subtype

We assessed the role of [18F]FDG-PET/CT in identifying and managing cancer of unknown primary site (CUP syndrome). We reviewed [18F]FDG-PET/CT scans of individuals with CUP syndrome recorded in clinical referral letters from 2012 to 2019. We evaluated the identification of primary tumor (PT) by [18F]FDG-PET/CT, according to histological subtype, and the impact on clinical management. The median age was 65 years, 36/64 males (56%). PTs were detected in 28/64 (44%) patients. Detection was significantly lower in patients with squamous cell carcinoma (SCC) than with other histologies combined, p = 0.034. Mean age, mean SUVmax (10.6 ± 6.0) and organ involvement were similar between patients with and without discovered PTs; and between patients with SCC and with other histologies combined. However, those with SCC were less likely than the others to present with multi-lesion involvement, p < 0.001. [18F]FDG-PET/CT interpretations apparently affected treatment of 8/28 (29%) patients with PT detected, and in none of the 35 whose PT was not discovered, p < 0.001. [18F]FDG-PET/CT appeared helpful in detecting PT in almost half the patients with CUP syndrome; the lowest rate was for patients with SCC pathology. PET/CT showed limited overall value in guiding clinical management, however benefited those with discovered PT.

Clinical value of 68Ga-DOTA-SSTR PET/CT in the diagnosis and detection of neuroendocrine tumors of unknown primary origin: a systematic review and meta-analysis

BACKGROUND

The ability of ⁶⁸Ga-DOTA-SSTR to detect the primary sites of neuroendocrine tumors (NETs) remains undetermined, and the clinical benefit of this imaging agent is not clear.

PURPOSE

To evaluate the diagnostic accuracy of ⁶⁸Ga-DOTA-SSTR for carcinoma unknown primary (CUP) neuroendocrine tumors and to further analyze the detection rate of ⁶⁸Ga-DOTA-SSTR for primary and metastatic sites.

MATERIAL AND METHODS

A comprehensive literature search of PubMed/MEDLINE and ScienceDirect was performed in October 2019 in accordance with the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines. We critically reviewed all studies based on the PICOS criteria. QUADAS-2 was used to evaluate the quality of the methodology of the included studies.

RESULTS

A total of 10 studies (484 patients, mean age = 56.6 ± 4.3 years) were included in the study. The pooled sensitivity and specificity of ⁶⁸Ga-DOTA-SSTR in identifying CUP-NETs were 82% and 55%, respectively. The area under the receiver operating characteristic curve was 69%. Regarding metastasis sites, ⁶⁸Ga-DOTA-SSTR found the most metastases in the liver (57.9%), followed by the lymph nodes (22.8%), bones (12.8%), lung (2.8%), and others (1.7%). The pooled detection rate of ⁶⁸Ga-DOTA-SSTR for CUP-NETs was 61%.

CONCLUSION

The present study demonstrated the high diagnostic sensitivity of ⁶⁸Ga-DOTA-SSTR for CUP-NETs. ⁶⁸Ga-DOTA-SSTR PET/CT was highly effective in locating the primary and metastatic sites of CUP-NETs.

[Radiological aspects in the diagnostics of pathological fractures]

Radiological diagnostics play a key role in the identification and assessment of pathological fractures. Conventional projection radiography is still the mainstay of imaging investigations. With knowledge of the patient history, the morphology and location of a fracture as well as concomitant findings, such as osteolysis or periosteal reactions can add valuable information on the origin of the fracture. Magnetic resonance imaging (MRI) is the imaging modality of choice for the local diagnostic work-up as it provides insights into the medullary cavity and visualizes potential extraosseous tumor tissue in the fracture zone. Computed tomography (CT) imaging provides valuable information on the morphological features of fractures and is useful for the planning of the surgical approach. Furthermore, it is the modality of choice for whole-body staging. In most cases of pathological fractures without a history of malignancy, a biopsy and histological work-up is recommended.

Sjögren's syndrome with nervous system injury combined with pulmonary and osseous cryptococcosis: a case report

BACKGROUND

Sjögren's syndrome is a common autoimmune disease that can involve the nervous system, but rarely both the central and peripheral. Long-term use of high-dose corticosteroids and immunosuppressants are the main risk factors for Cryptococcus infection in patients with Sjögren's syndrome, of which pulmonary infection is the most common, while multiple bone infections are rare.

CASE PRESENTATION

A 46-year-old Chinese woman with a 2-year history of Sjögren's syndrome presented to our hospital with numbness of limbs, shortness of breath, and weakness. Blood immunochemistry showed that antinuclear antibody (1:640), anti-Sjögren's syndrome-A antibodies, and anti-centromere antibodies were strongly positive. Cranial magnetic resonance imaging revealed multiple demyelinating lesions in the white matter of bilateral cerebral hemispheres. Electromyography indicated serious peripheral nerve injury, especially in lower limbs. Computed tomography scan of lumbar vertebral displayed multiple high-density shadows, and the corresponding vertebrae on magnetic resonance imaging showed abnormal low signal intensity on T1 and T2 sequences. Positron emission tomography-computed tomography showed multiple lesions with high 18F-fluorodeoxyglucose uptake in lung and vertebral bodies. Both lung and bone biopsies suggested Cryptococcus infection, with the diagnosis of Sjögren's syndrome with nervous system injury combined pulmonary and osseous cryptococcosis. She took a reduced dose of prednisone about 10 mg/day, terminated mycophenolate mofetil, and began to take immunoglobulin of 0.4 g/kg/day intravenously for 5 days, fluconazole (400 mg/day) for 6 months. Within 3 weeks, her chest radiography showed a marked improvement, and 3 months later, the pulmonary lesions disappeared on her computed tomography scan.

CONCLUSIONS

This case exhibits an extremely rare condition of neural involvement in Sjögren's syndrome combined with pulmonary and osseous cryptococcosis. This report also highlights the crucial role of detailed clinical examination, serologic markers, and biopsy in avoiding misdiagnosis. Currently, there is no guideline for this situation; in this case, we controlled the disease successfully with antifungal drugs and adequate gamma globulin, followed by an appropriate dose of corticosteroids.

Role of FDG PET/CT for detection of primary tumor in patients with extracervical metastases from carcinoma of unknown primary

AIM

To explore the diagnostic performance of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) to detect the primary tumor site in patients with extracervical metastases from carcinoma of unknown primary (CUP). We evaluated patient outcomes as overall survival (OS).

MATERIALS AND METHODS

In a single-center, retrospective study (2005-2019), patients with extracervical metastases from CUP underwent FDG PET/CT to detect primary tumor sites. The final diagnosis was based on histopathology/or clinical follow-up of at least 12 months.

RESULTS

A total of 83 patients [Male 41 (49%), mean age 59 ± 14 years, range: 32-83 years] fulfilled the inclusion/exclusion criteria and were enrolled for analysis. The primary tumor was detected in 36 out of 83 (43%) patients based on histopathology/or clinical follow-up. PET/CT suggested the primary tumor site in 39 (47%) patients with diagnostic accuracy of 87%, sensitivity 89%, specificity 85%, PPV 82%, NPV 91% and detection rate 39%. Patients with oligometastases (<3) (2.16 years, 1.04-2.54) and primary unidentified (1 year, 0.34-2.14) had longer median survival time compared to the patients with multiple metastases (0.67 years, 0.17-1.58, p = 0.009) and primary identified (0.67 years,0.16-1.33, p = 0.002). The SUVmax of the primary or metastatic lesions with maximum uptake was not significantly related to survival.

CONCLUSIONS

PET/CT could reveal the primary tumor site in 39% of the patients. It demonstrated the metastatic disease burden and distribution in patients with 'primary obscured', which directs management. Patients with multiple metastases and primary identified had a poorer prognosis. In patients with primary unidentified after PET/CT, a further search was futile.

[Cervical CUP syndrome]

The term CUP syndrome (cancer of unknown primary) refers to a multifaceted clinical picture in which the affected patients have lymph node and/or distant metastases without the location of the primary tumor being known. The criteria of CUP syndrome are fulfilled if a histologically or cytologically confirmed malignancy is present without a detectable primary tumor after completion of the primary diagnosis. Due to the usually poor prognosis and the manifold appearance, which often does not allow a standardized therapy, cervical CUP syndrome makes specific demands on clinical and imaging diagnostics. Using modern techniques such as positron emission tomography-computed tomography (PET-CT), imaging plays a key role in the detection of a possible occult primary tumor as well as in staging and prognosis assessment.

Cancer of unknown primary

Cancers of unknown primary (CUPs) are histologically confirmed, metastatic malignancies with a primary tumor site that is unidentifiable on the basis of standard evaluation and imaging studies. CUP comprises 2-5% of all diagnosed cancers worldwide and is characterized by early and aggressive metastasis. Current standard evaluation of CUP requires histopathologic evaluation and identification of favorable risk subtypes that can be more definitively treated or have superior outcomes. Current standard treatment of the unfavorable risk subtype requires assessment of prognosis and consideration of empiric chemotherapy. The use of molecular tissue of origin tests to identify the likely primary tumor site has been extensively studied, and here we review the rationale and the evidence for and against the use of such tests in the assessment of CUPs. The expanding use of next generation sequencing in advanced cancers offers the potential to identify a subgroup of patients who have actionable genomic aberrations and may allow for further personalization of therapy.

Adrenal and Bone Metastases as the Initial Presentation of Endometrial Carcinoma Diagnosed by 18F-FDG PET/CT

Adrenal and bone metastases as the initial presentation of endometrial carcinoma are rare. We report a case of endometrial carcinoma in a 47-year-old woman with initial manifestation as right chest wall pain, which was suspected as adrenal cortical carcinoma with rib metastasis after diagnostic CT scan. However, uterine and pelvic bone lesions were revealed by staging FDG PET/CT. Eventually, endometrial carcinoma with adrenal and bone metastases was confirmed pathologically.

68Ga-PSMA PET/CT and 18F-FDG PET/CT in Renal Cell Carcinoma

Recent case reports and series have demonstrated the usefulness of Ga/F-PSMA PET/CT in restaging recurrent renal cancer after nephrectomy. We presented a case of a patient with renal mass who had undergone both F-FDG and Ga-PSMA PET/CT for diagnosis and staging. Concordant tracer uptake in the primary tumor and metastatic lesions was demonstrated by both radiotracers. Final histopathological reports revealed clear cell renal cell carcinoma. Furthermore, unusual left metacarpal bone metastasis was also detected.

Clinical Impact of F-18 FDG PET-CT on Biopsy Site Selection in Patients with Suspected Bone Metastasis of Unknown Primary Site

Purpose

We investigated the clinical role of F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) in the identification of the primary site and the selection of the optimal biopsy site in patients with suspected bone metastasis of unknown primary site.

Methods

The patients with suspected bone metastasis who underwent PET-CT for evaluation of primary site were enrolled in this study. The primary sites were identified by the histopathologic or imaging studies and were classified according to the FDG uptake positivity of the primary site. To evaluate the guiding capability of PET-CT in biopsy site selection, we statistically analyzed whether the biopsy site could be affected according to the presence of extra-skeletal FDG uptake.

Results

Among 74 enrolled patients, 51 patients had a metastatic bone disease. The primary site was identified in 48 of 51 patients (94.1%). Forty-six patients were eligible to test the association of clinical choice of biopsy site with PET positivity of extra-skeletal lesion. The extra-skeletal biopsies were done in 42 out of 43 patients with positive extra-skeletal uptake lesions. Bone biopsies were inevitably performed in the other three patients without extra-skeletal uptake lesions. The association came out to be significant (Fisher's exact test, P < 0.001).

Conclusion

F-18 FDG PET-CT significantly contributed not only to identify the primary site but also to suggest optimal biopsy sites in patients with suspected bone metastasis.

Microbial communities from arid environments on a global scale. A systematic review

Arid environments are defined by the lack of water availability, which is directly related to the mean annual precipitation (MAP), and high values of solar irradiation, which impacts the community composition of animals, plants, and the microbial structure of the soil. Recent advances in NGS technologies have expanded our ability to characterize microbiomes, allowing environmental microbiologists to explore the complete microbial structure. Intending to identify and describe the state-of-the-art of bacterial communities in arid soils at a global scale, and to address the effect that some environmental features may have on them, we performed a systematic review based on the PRISMA guideline. Using a combination of keywords, we identified a collection of 66 studies, including 327 sampled sites, reporting the arid soil bacterial community composition by 16S rDNA gene high-throughput sequencing. To identify factors that can modulate bacterial communities, we extracted the geographical, environmental, and physicochemical data. The results indicate that even though each sampled site was catalogued as arid, they show wide variability in altitude, mean annual temperature (MAT), soil pH and electric conductivity, within and between arid environments. We show that arid soils display a higher abundance of Actinobacteria and lower abundance of Proteobacteria, Cyanobacteria, and Planctomycetes, compared with non-arid soil microbiomes, revealing that microbial structure seems to be strongly modulated by MAP and MAT and not by pH in arid soils. We observed that environmental and physicochemical features were scarcely described among studies, hence, we propose a reporting guideline for further analysis, which will allow deepening the knowledge of the relationship between the microbiome and abiotic factors in arid soil. Finally, to understand the academic collaborations landscape, we developed an analysis of the author's network, corroborating a low degree of connectivity and collaborations in this research topic. Considering that it is crucial to understand how microbial processes develop and change in arid soils, our analysis emphasizes the need to increase collaborations between research groups worldwide.

FDG PET Hybrid Imaging

Molecular imaging with positron emission tomography (PET) using tumour-seeking radiopharmaceuticals has gained wide acceptance in oncology with many clinical applications. The hybrid imaging modality PET/CT (computed tomography) allows assessing molecular as well as morphologic information at the same time. Therefore, PET/CT represents an efficient tool for whole-body staging and re-staging within one imaging modality. In oncology, the glucose analogue 18-F-fluorodeoxyglucose (FDG) is the most widely used PET/CT radiopharmaceutical in clinical routine. FDG PET and FDG PET/CT have been used for staging and re-staging of tumour patients in numerous studies. This chapter will discuss the use and the main indications of FDG PET/CT in oncology with special emphasis on lung cancer, lymphoma, head and neck cancer, melanoma and breast cancer (among other tumour entities). A review of the current literature is given with respect to primary diagnosis, staging and diagnosis of recurrent disease. Besides its integral role in diagnosis, staging and re-staging of disease in oncology, there is increasing evidence that FDG PET/CT can be used for therapy response assessment (possibly influencing therapeutic management and treatment planning) by evaluating tumour control, which will also be discussed in this chapter.

Advances in the management of brain metastases from cancer of unknown primary

Cancer of unknown primary accounts for 3-5% of all cancers for which an adequate investigation does not identify the primary tumor. The particular subset of brain metastasis in cancer of unknown primary (BMCUP) is a clinical challenge that lacks standardized diagnostic and therapeutic options. It is diagnosed predominantly in male patients in the sixth decade of age with complaints of headache, neurological dysfunction, cognitive and behavioral disturbances and seizures. The therapeutic approach to patients with BMCUP relies on local control and systemic treatment. Surgery or stereotactic radiosurgery and/or whole brain radiation therapy seems to be the cornerstone of the treatment approach to BMCUP. Systemic therapy remains essential as cancers of unknown primary are conceptually metastatic tumors. The benefits of chemotherapy were disappointing whereas those of targeted therapies and immune checkpoint inhibitors remain to be evaluated. In this Review, we address the advances in the diagnosis and treatment of BMCUP.

CUP Syndrome-Metastatic Malignancy with Unknown Primary Tumor

BACKGROUND

2-4% of newly diagnosed cases of malignant disease involve cancer of unknown primary (CUP). This mixed entity is one of the 6 most common types of malignant disease in Germany. Highly refined treatment strategies can now be offered to patients with CUP.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed with an emphasis on articles from the past decade. The current guidelines and recommendations of specialty societies were also considered in the evaluation.

RESULTS

CUP most commonly manifests itself as metastases to the lymph nodes, lungs, liver, or bones. With the aid of imaging studies, including functional hybrid imaging and further medical examination, a primary tumor can be discovered in up to 40% of patients initially diagnosed with CUP. Immunohistochemistry guided by histomorphology often enables precise characterization of the lesion and can be supplemented, in selected cases, by molecular-genetic diagnostic evaluation. The most commonly detected types of primary tumor are cancers of the lung, pancreas, liver, and biliary system. For patients with local metastases, surgical resection or radiotherapy with curative intent is usually indicated, sometimes in the framework of a multimodal treatment concept. The median 2-year survival of patients with disseminated CUP is only 20%. For such patients, specific types of systemic therapy are recommended on the basis of the diagnostic characterization of the disease. Immune-modulatory antibodies can be effective, particularly in the treatment of CUP that has been characterized with biomarkers, but should still be considered experimental at present.

CONCLUSION

A combination of conventional and innovative diagnostic methods enables the provision of highly refined therapeutic strategies to patients with CUP who are undergoing treatment in interdisciplinary cancer centers.

Detection efficiency of 18F-flourodeoxyglucose positron emission tomography/computed tomography for primary tumors in patients with carcinoma of unknown primary

Carcinoma of unknown primary (CUP) is defined as biopsy proven tumor metastases that remains unidentified after a thorough diagnostic evaluation. The purpose of this study was to find the detection efficiency of ¹⁸F-flourodeoxyglucose positron emission tomography/computed tomography (¹⁸FDG PET/CT) in patients with CUP. This prospective study was conducted at PET/CT Section of Department of Radiology, Aga Khan University Hospital Karachi, Pakistan from August 2017 to January 2018. Patients with a history of CUP referred for ¹⁸FDG PET/CT scan for detection of primary sites during the study were recruited. ¹⁸FDG PET/CT scan was acquired using standardized protocol, and patients with suspected primary sites underwent biopsies. Scan findings and biopsy results were analyzed to find the detection rate, sensitivity, area under curve (AUC), and positive predictive value (PPV). As no biopsy was performed in negative scan, true negative, and specificity could not be calculated. During the study, 46 consecutive patients with CUP were included. Mean age of cohort was 58 ± 17 years (63% male and 37% female) having a mean body mass index of 24.70 ± 4.97 kg/m². Thirty-four patients (34/46) found to have a hypermetabolic focus suggestive of the primary tumor with known metastatic sites and subjected to biopsy which turned out to be positive in 26/34 patients (true positive). The primary tumor was detected in gastrointestinal and hepatobiliary in 8 (17%), head and neck in 6 (13%), genitourinary 4 (09%), lung 3 (06%), and miscellaneous sites in 5 (11%) patients. Detection rate, sensitivity and PPV of ¹⁸FDG PET/CT were 57%, 68%, and 76%, respectively. Remaining 12/46 patients with negative ¹⁸FDG PET/CT for primary focus did not have biopsy. Receiver operating character curve revealed fair diagnostic strength of ¹⁸FDG PET/CT for detecting unknown primary (AUC 0.667; P = 0.054; standard error = 0.083; confidence interval: 0.504–0.830). We conclude that ¹⁸FDG PET/CT is an effective tool for detecting primary tumor in patients with CUP and its upfront use could preclude the use of many futile diagnostic procedures. Furthermore, higher resolution scanners and acquiring delayed images in patients with negative study could reduce false-negative results in patients with CUP.

Solitary colonic metastasis from primary lung adenocarcinoma first presenting as intestinal obstruction: A case report

RATIONALE

The brain, liver, adrenal glands, and bone are the most common sites of metastatic disease in patients with lung cancer. Symptomatic gastrointestinal metastases are rare. In the present report, we describe a rare case of a patient with intestinal obstruction due to solitary colonic metastasis from primary lung adenocarcinoma, wherein the intestinal obstruction was the first symptom of lung cancer.

PATIENT CONCERNS

A 74-year-old man was admitted to the emergency room with abdominal pain and vomiting, and abdominal computed tomography (CT) indicated obstruction of the ascending colon due to a huge mass.

DIAGNOSIS

The ascending colon cancer was found to be a metastatic adenocarcinoma based on the results of the pathology report. Chest CT and positron emission tomography-CT were performed to identify the cancer origin site. Moreover, immunohistochemical staining of the tissue specimen for thyroid transcription factor 1, cytokeratin 7 (CK7), and CK20 and CT-guided gun biopsy of the lung mass confirmed the presence of an adenocarcinoma that originated from the lung.

INTERVENTION

Right hemicolectomy was performed as the primary treatment.

OUTCOMES

The patient recovered without any problems due to the surgery itself. However, malignant pleural effusion deteriorated, and no additional palliative chemotherapy was performed.

LESSONS

Patients with malignant bowel obstruction along with lung infiltration should be suspected of not only colon cancer with lung metastasis, but also lung cancer with colon metastasis.

Role of 18F-FDG PET/CT in patients without known primary malignancy with skeletal lesions suspicious for cancer metastasis

BACKGROUND

When subjects without a known malignancy present with suspicious skeletal lesions, differential diagnosis and primary cancer identification is important. Here, we investigated the role of FDG PET/CT in this clinical situation.

METHODS

We enrolled 103 patients with no known malignancies who were referred for FDG PET/CT because of bone lesions that were suspicious for cancer metastasis. Each extra-skeletal FDG lesion was categorized as consistent with primary cancer or with metastasis based on the distribution and pattern of all abnormal lesions in the individual.

RESULTS

Final diagnosis revealed that bone lesions represented cancer metastasis in 75 patients (72.8%). In the remaining 28 patients (27.2%), they were from other causes including multiple myeloma or lymphoma, malignant primary bone tumor, and benign bone disease. PET/CT indicated a primary cancer in 70 patients (68.0%). This was the correct primary site in 46 cases and the incorrect site in 13 cases (including 6 cases with cancer of unknown primary, CUP). In the remaining 11 cases, the bone lesions were due to other causes. PET/CT did not indicate a primary cancer in 33 patients (32.0%). Of these cases, 17 did not have a primary cancer, 8 had CUP, and 8 had primary cancers that were missed. Thus, PET/CT had a sensitivity of 61.3% and specificity of 60.7% for primary cancer identification in the entire population. Excluding patients with CUP, PET/CT sensitivity was 75.4%. PET/CT also provided information useful for recognizing multiple myeloma and benign bone disease as the cause of the skeletal lesions.

CONCLUSIONS

In patients without known malignancies with suspected skeletal cancer metastasis, FDG PET/CT can help identify the primary cancer and provide useful information for differential diagnosis.

Diagnostic value of 18F-fluordesoxyglucose positron emission tomography for patients with brain metastasis from unknown primary site

BACKGROUND

In 30% of patients with brain metastasis (BM), neurological symptoms are the first clinical manifestation of systemic malignancy, referred to as BM from cancer of unknown primary site (BM-CUPS). Here, we define the diagnostic value of ¹⁸F-fluordesoxyglucose positron emission tomography (FDG-PET/CT) in the workup of BM-CUPS.

METHODS

We screened 565 patients operated for BM at the University Hospital Zurich and identified 64 patients with BM-CUPS with data on both FDG-PET/CT and contrast-enhanced chest/abdomen computed tomography (CT) available at BM diagnosis. A cohort of 125 patients with BM-CUPS from Lille and Vienna was used for validation.

RESULTS

FDG-PET/CT was not superior to chest/abdomen CT in localising the primary lesion in the discovery cohort, presumably because most primary tumours were lung cancers. However, FDG-PET/CT identified additional lesions suspicious of extracranial metastases in 27 of 64 patients (42%). The inclusion of FDG-PET/CT findings shifted the graded prognostic assessment (GPA) score from 3 with CT alone to 2.5 for PET/CT (p = 3.8 × 10^-5, Wilcoxon's test), resulting in a predicted survival of 5.3 versus 3.8 months (p = 6.1 × 10^-5; Wilcoxon's test). All observations were confirmed in the validation cohort.

CONCLUSIONS

Lung cancers are the most common primary tumour in BM-CUPS; accordingly, CT alone shows similar overall sensitivity for detecting the primary tumour as FDG-PET/CT. Yet, FDG-PET/CT improves the accuracy of staging by detecting more metastases, reflected by decreased GPA scores and decreased predicted survival. Therefore, randomised trials on patients with BM should standardise methods of staging, notably when stratifying for GPA.

Mandibular metastasis as the first clinical indication of occult lung adenocarcinoma with multiple metastases: A case report

RATIONALE

Although metastases to the oral and maxillofacial region (OMR) are rare, the lung is the most common primary site metastasizing to the OMR.

PATIENT CONCERNS

An 83-year-old woman presented with reports of trismus, occlusal discomfort, swelling, and spontaneous pain in the right buccal region. Despite the absence of abnormal chest imaging findings, immunohistochemical analysis of biopsy specimens of the mandible and the thyroid indicated that the patient had multiple metastases from a lung poorly differentiated adenocarcinoma.

DIAGNOSES

Metastases to the OMR and the thyroid from an undiscovered lung adenocarcinoma.

INTERVENTIONS

Gefitinib was started as first-line chemotherapy, and zoledronic acid was administered for bone metastases.

OUTCOMES

Follow-up imaging examinations showed ossification and deformation of the right mandibular ramus and the condylar process. Although 2 years have passed since the first visit to our hospital, lung lesions have not been confirmed by imaging examinations.

LESSONS

Clinicians should consider the possibility that symptoms in the OMR may be the first clinical sign of an undiscovered distant primary tumor, and the primary tumors may not be detected by imaging examinations even when metastases to the OMR are revealed.